Potassium iodide is a salt made up of the minerals potassium (K) and iodine (I). Its chemical formula is “KI.”

Potassium iodide is a medication and, when used properly, it can help protect the thyroid gland from radiation exposure caused by a nuclear emergency.

During a nuclear emergency, radioactive iodine may be released into the air. Radioactive iodine can negatively affect your thyroid and increase the risk of thyroid problems, including cancer.

Potassium iodide contains nonradioactive iodine, which can reduce the risk of thyroid damage. However, you should take it only during an emergency, not as a daily supplement.

Read on to learn how potassium iodide works, who should use it, and when you may need to use it.

Potassium iodide protects the thyroid by blocking the absorption of radioactive iodine. This is known as iodine thyroid blocking.

When you take potassium iodide, your thyroid becomes saturated with nonradioactive iodine. This causes your thyroid to “fill up.”

As a result, your thyroid will not be able to absorb any type of iodine for the next 24 hours. Excess iodine, either nonradioactive or radioactive, will leave your body via your urine. This can help reduce the risk of thyroid cancer due to radioactive iodine.

It’s important to note that potassium iodide protects only your thyroid. It does not protect the rest of your body because it’s not a general radioprotective agent, according to the Food and Drug Administration (FDA). As such, it doesn’t prevent radioactive iodine from entering your body — it only stops your thyroid from absorbing the iodine.

Additionally, potassium iodide does not protect against external radiation exposure or other radioactive compounds.

Potassium iodide is used during nuclear emergencies. You should take it only when public health officials specifically say to do so.

To protect your thyroid, you must take potassium iodide within a certain time frame. According to the World Health Organization, the optimal time frame for maximum benefit is less than 24 hours before an expected exposure and up to 2 hours after the exposure. Taking it more than 24 hours after the exposure will not protect your thyroid.

People over age 40 have a low risk of developing radiation-induced thyroid cancer, so they may need a smaller dose than younger people or may not need to take potassium iodide at all.

The risk is higher in children and infants. As a result, children and infants will likely need to take potassium iodide. It’s safe for these age groups when taken at the proper dose.

In an emergency, public health officials will determine which age groups should take the medication.

When taking potassium iodide, it’s crucial to take the exact dose recommended. According to the FDA, the recommended doses for different groups are as follows:

  • Infants 1 month old and younger: 16 milligrams (mg)
  • Children over 1 month old and up to age 3: 32 mg
  • Children over age 3 and up to age 12: 65 mg
  • Adolescents over age 12 and up to age 18: 65 mg
  • Adults ages 18 and older: 130 mg
  • People who are pregnant or nursing: 130 mg

You should keep taking potassium iodide once a day until the health department says to stop or you are outside of the emergency area. Never take potassium iodide more often than instructed. This will not provide extra protection. Taking too much potassium iodide can lead to severe illness or death.

Potassium iodide is not an “anti-radiation” supplement. You should never use it as a preventive measure against radiation exposure. You should use it only during or after an expected exposure and only if public health officials direct you to do so.

Potassium iodide will work only if you take it at the right time and in the right dose. Taking it continuously when there’s no risk of radiation exposure can lead to serious complications.

In certain situations outside of nuclear emergencies, healthcare professionals may prescribe potassium iodide for conditions such as severe hyperthyroidism and cutaneous inflammatory dermatoses or to protect the thyroid when using radiopharmaceutical agents.

People with low iodine intake may also use it as a dietary supplement. This is more common in developing countries. However, this should be done only under the guidance of a healthcare professional and is usually done to reduce radiation exposure.

When taken correctly, potassium iodide is unlikely to cause side effects. The benefits of thyroid protection during nuclear exposure outweigh the potential risks.

If side effects do occur, they may include:

  • mild allergic reaction
  • skin rash
  • upset stomach
  • swollen salivary glands
  • metallic taste in your mouth
  • burning sensation in your mouth and throat
  • soreness in your teeth and gums

Potassium iodide is available without a prescription. You can order it from online retailers that specialize in emergency preparedness supplies.

In the case of a nuclear emergency, your local health officials will distribute potassium iodide to the community. You may also be able to find potassium iodide at:

  • schools
  • hospitals
  • pharmacies
  • fire and police stations
  • evacuation centers
  • city or town halls

Your local news channels and radio stations will indicate where you can get it when necessary.

Again, take potassium iodide only if you’ve been exposed to radiation and healthcare professionals have specifically told you to take it.

Potassium iodide is a medication that can help protect your thyroid during radiation emergencies. It contains nonradioactive iodide, which your thyroid absorbs. This prevents the absorption of radioactive iodine, potentially reducing the risk of thyroid cancer.

it’s important to take potassium iodide only when instructed by local health officials and only in the recommended dose. Potassium iodide is not a daily supplement and will not offer extra protection if taken more frequently.

If you have questions or concerns about potassium iodide, consult a healthcare professional. They can provide personalized guidance for you and your family.